The significant improvements in data processing achieved over the last decade have led to the wide-spread availability of computers and FAX machines. Both computers, via modems, and FAX machines communicate over telephone lines. The simplest method for accommodating these devices utilizes separate telephone lines for each device. Hence, these devices have led to an increased demand for telephone lines. While this solution is simple to implement, the cost of installation and monthly service fees often exceeds the cost of the hardware attached to the telephone lines.
The prior art has attempted to solve this cost problem by providing an interface box which connects to a telephone line and provides separate ports for connecting voice, FAX, and modem lines. When an incoming call is received, the interface box answers the call and tries to determine the nature of the call. If the interface box detects a CNG tone, it assumes that the call is for the FAX machine and connects the incoming telephone line to the FAX port. If the interface box detects DTMF tones, it assumes that the incoming call is for a modem and connects the incoming telephone line to the modem port. If the interface box does not detect either a CNG tone or DTMF tones, the interface box assumes the incoming call is a conventional telephone call and connects the incoming telephone line to the telephone port. The interface box then generates a conventional telephone ringing signal on the telephone port until such time as the telephone connected thereto goes off hook or the calling party hangs up.
While this type of prior art interface box allows all three types of devices to be connected to an incoming telephone line, it has a number of problems. First, not all FAX machines generate CNG tones. Hence, a call from one of these FAX machines is directed to the voice port. As a result, the FAX connection is not made and the FAX will not be delivered unless a person is present to receive the call and manually direct it to the FAX machine.
Second, the "style" of the incoming ring signal is not reproduced on the voice port when the interface box determines that the incoming call is a conventional telephone call. In prior art interface boxes, a fixed ring pattern is generated on the voice port. In many telephone systems, the incoming ring pattern alerts the recipient of the type of telephone call. For example, in some PBX systems, a different ring pattern is used for outside calls then for calls from another extension on the PBX. In addition, some telephone companies provide specialized services in which call originating from a predetermined list of telephone numbers have different ring patterns. This alerts the recipient to the fact that the incoming call is from one of a select group of callers.
Third, it is difficult to regain control of the incoming telephone line in case of emergency if the interface box has connected the incoming telephone line to the FAX or modem ports. While many of these prior art interface boxes have reset switches on the interface box for this purpose, the interface box may be located at some distance from the voice handset. In addition, a user who is not familiar with the particular interface box often has difficulty determining the reset procedure. Some interface boxes are constructed on circuit cards in personal computers. In these cases, a user wishing to take control of the line must either know how to reset the particular software or cycle down the entire computer.
Fourth, if a user picks up the telephone handset while the interface box is attempting to identify a call, errors in the identification of the call type often result. This situation can arise in at least two situations. First, the user may just happen to pick up the phone to make an outgoing call during the time the interface box is attempting to identify an incoming call. Second, the user may note that an incoming call has been received and wish to intercept the call if it is a voice call to prevent the call being lost due to the delays inherent in identifying a call or an interface box malfunction.
Broadly, it is the object of the present invention to provide an improved telephone interface box for connecting an incoming telephone line to a FAX machine and voice hand set.
It is another object of the present invention to provide a telephone interface box which mimic's the ring style of the incoming telephone call when the interface box determines that the incoming call is a voice transmission.
It is a still further object of the present invention to provide a telephone interface box which may be reset without a knowledge of the location of the interface box or the details of software running the interface box.
It is yet another object of the present invention to provide a telephone interface box which does not depend on CNG tones to identify an incoming FAX transmission.
It is a still further object of the present invention to provide a telephone interface box which allows the user to pick up the handset during call identification without introducing errors into the call identification process.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.